The invention relates to a method and a device for determining the transmittance of a flat-glass substrate with a measuring device, with which light of at least one light source is guided from one side of the flat-glass substrate through the flat-glass substrate to the opposite side of the flat-glass substrate, where it is captured by at least one receiving unit. The transmittance of the flat-glass substrate can then be determined by means of a comparison between the intensity of the light emitted by the light source and the light incident upon the receiving unit.
In the manufacture of flat glass, a continuous transmittance must be achieved as one of various quality requirements. The thickness of the glass, for example, is another essential parameter. Particularly when using flat glass as solar glass, which is a special glass for thermal solar collectors and photovoltaics, a continuous transmittance has to be observed. In order to be able to use the incident solar radiation optimally, as high a transmittance as possible of the supported glass layer has to be ensured.
In this case, flat glass provided for use as solar glass has particularly high requirements with respect to continuous homogeneity. With regard to flat glass as such, a distinction is made between float glass and rolled glass, the type of glass depending on the production process chosen in each case. Both types of glass are used as solar glass, it being possible to manufacture planar glass in a float process, and structured glass (structural glass) in a rolling process. Typically, both production processes are endless continuous processes in which the glass melt is permanently pulled in a flat manner onto a tin bath or rolled through rotating rollers. The glass is cut to size only after passing through a cooling system.